JP5149355B2 - Spot welding method and spot welding apparatus - Google Patents

Description

  The present invention relates to a spot welding method and a spot welding apparatus for spot welding a member to be welded in a plate assembly in which plate materials having different thicknesses are overlapped.

  In general, for joining plate materials such as stacked steel plates, a large current is passed between the welding electrodes for a certain period of time while applying pressure between a pair of welding electrodes, and the nugget is raised to a substantially melting temperature. Spot welding to form is widely performed.

  In spot welding, when the applied pressure and energization time applied by both welding electrodes are constant, the nugget diameter gradually increases as the current increases. This causes the scattering of the molten metal. In other words, scattering is a phenomenon of molten metal explosion due to overheating of the joint, resulting in voids, cracks, etc. in the nugget, resulting in discontinuities in the shape and metal structure of the nugget, and a marked decrease in the thickness of the joint It becomes a factor of strength reduction. On the other hand, when the current is too small, the nugget becomes small and sufficient bonding strength cannot be obtained. In addition, when the applied pressure is small, the contact area between the plate members is reduced, the current density is increased, and this causes scattering due to overheating. On the other hand, when the applied pressure is too large, the contact area of the joint is increased, the current density is lowered, and the heat generation amount is reduced. As a result, the nugget is small and the welding strength is reduced.

  Here, as shown in FIG. 18 (a), the member to be welded 100 in which three sheets of a thin plate 101 having a low rigidity, a first thick plate 102 thicker than the thin plate 101 and having a higher rigidity, and a second thick plate 103 are overlapped is spotted. When welding, the movable side electrode 121 and the fixed side electrode 122 cover the thin plate 101 and the first thick plate 102 and between the first thick plate 102 and the second thick plate 103 without any gap. When energized by the power source 123 with the welding member 100 interposed therebetween, the current density in the energization path between the movable electrode 121 and the fixed electrode 122 becomes substantially uniform, and a good nugget is formed from the thin plate 101 to the second thick plate 103. The required welding strength can be obtained.

  However, in practice, when the member to be welded 100 is sandwiched and pressed by the movable side electrode 121 and the fixed side electrode 122, the thin plate 101 and the first thick plate 102 having low rigidity bend upward, and the thin plate 101 and the first plate A gap is generated between the first thick plate 102 and between the first thick plate 102 and the second thick plate 103. In this case, the contact area between the movable electrode 121 and the thin plate 101 is increased by the bending of the thin plate 101, whereas between the thin plate 101 and the first thick plate 102 and between the first thick plate 102 and the second thick plate 103. The contact area of the joint is reduced by the gap.

  For this reason, the current density at the junction between the movable electrode 121 and the fixed electrode 122 is higher on the second thick plate 103 side than on the thin plate 101 side, and the first thick plate 102 is between the thin plate 101 and the first thick plate 102. And the second thick plate 103 generate more local heat.

As a result, the nugget 105 is formed at the junction of the first plank 102 First, as shown with the second plank 103 in FIG. 18 (a), gradually nugget 105 increases soon as 18 (b), The thin plate 101 and the first thick plate 102 are welded. However, the amount of penetration between the thin plate 101 and the first thick plate 102 is small, the welding strength is unstable, the thin plate 101 may be peeled off, and the welding quality varies. This problem is particularly noticeable because the nugget 105 is less likely to reach between the thick plate 102 and the thin plate 101 as the first thick plate 102 and the second thick plate 103 are thicker.

  Similarly, the reason why the amount of penetration between the thin plate 101 and the first thick plate 102 is small and the welding strength becomes unstable is that the thin plate 101 is thin, so that heat is drawn to the movable side electrode 121 by the contact of the movable side electrode 121. In other words, the temperature on the thin plate 101 side does not rise, and the nugget 105 may be difficult to form.

  As a countermeasure, for example, there is a spot welding method disclosed in Patent Document 1. In this spot welding method, as shown in FIG. 19, when spot welding is performed on the member to be welded 100 in which the thin plate 101, the first thick plate 102, and the second thick plate 103 are overlapped, the movable side that contacts the thin plate 101 side is used. By making the tip diameter of the electrode 121 smaller than the tip diameter of the fixed side electrode 122 in contact with the second thick plate 103 side, the contact area between the thin plate 101 and the movable side electrode 121 is reduced to the second thick plate 103 and the fixed side. The contact area with the electrode 122 is made smaller. As a result, the current density in the energization path between the movable electrode 121 and the fixed electrode 122 gradually decreases from the movable electrode 121 side toward the fixed electrode 122. As a result, the amount of heat generated between the thin plate 101 and the first thick plate 102 increases, a good nugget is formed, and the welding strength between the thin plate 101 and the first thick plate 102 is improved.

  In addition, as shown in FIG. 20, the spot welding method disclosed in Patent Document 2 spot-welds a member to be welded 100 in which three plate materials of a thin plate 101, a first thick plate 102, and a second thick plate 103 are overlapped. When welding, the pressing force FU of the movable electrode 135 located on the thin plate 101 side is made smaller than the pressing force FL of the fixed electrode 134 positioned on the second thick plate 103 side, so that the thin plate 101 and the thick plate 102. And the contact resistance between the thick plates 102 and 103 is reduced, and when the movable side electrode 135 and the fixed side electrode 134 are energized, the thin plate 101 and the first thick plate 102 The amount of heat generated at the joint can be increased, and the welding strength between the thin plate 101 and the first thick plate 102 can be increased.

  As shown in FIG. 21, the spot welding apparatus used for carrying out this method has a spot welding apparatus 130 mounted on the wrist 126 of a welding robot 125, and the welding robot 125 is supported by a clamper 128. The spot welding device 130 is moved to each spot position of the member 100 to perform spot welding of the member 100 to be welded.

  The spot welding device 130 includes a base portion 132 supported by a linear guide 131 fixed to a support bracket 127 attached to the wrist portion 126 so as to be movable up and down. The base portion 132 has a C-shaped yoke 133 extending downward. The fixed side electrode 134 is provided at the tip of the lower end of the C-shaped yoke 133.

  A pressure actuator 136 such as a servo motor is mounted on the upper end of the base portion 132, and a movable side electrode 135 is attached to the lower end of a rod 137 that moves up and down by the pressure actuator 136 so as to face the fixed side electrode 134. . A servo motor 138 is mounted on the upper end of the support bracket 127, and the base portion 132 moves up and down via the ball screw mechanism by the operation of the servo motor 138.

  Here, in accordance with teaching data stored in advance in a controller (not shown), the pressure FU applied by the movable electrode 135 located on the thin plate 101 side is made smaller than the pressure FL applied by the fixed electrode 134 (FU <FL).

  In this way, in order to make the pressure FU applied by the movable electrode 135 smaller than the pressure FL applied by the fixed electrode 134 (FU <FL), the controller first moves the base portion 132 upward by the servo motor 138 to fix the pressure on the fixed side. The electrode 134 is brought into contact with the lower surface of the member to be welded 100, and the movable side electrode 135 is lowered by the pressure actuator 136 and brought into contact with the upper surface of the member to be welded 100. In this case, the pressure applied by the pressure actuator 136 acts equally on the movable side electrode 135, the base portion 132, and the fixed side electrode 134 via the C-shaped yoke 133.

  Next, the base portion 132 is pushed up by the servo motor 138. As the base portion 132 is pushed up, the pressing force FL of the fixed side electrode 134 is increased by the pushing amount of the base portion 132, and the pressing force FU by the movable side electrode 135 becomes smaller than the pressing force FL by the fixed side electrode 134 (FU < FL).

  As a result, when a current is passed between the movable side electrode 135 and the fixed side electrode 134, the current density at the junction between the thin plate 101 and the first thick plate 102 increases, and the amount of heat generated is between the first thick plate 102 and the second thickness. It increases relative to the amount of heat generated at the joint of the plate 103. As a result, a good nugget with no deviation in the amount of penetration is formed from the thin plate 101 to the second thick plate 103, and the welding strength can be ensured.

JP 2003-151468 A JP 2003-251469 A

  According to Patent Document 1, the movable side electrode 121 and the fixed side electrode are made smaller by making the distal end diameter of the movable side electrode 121 in contact with the thin plate 101 smaller than the distal end diameter of the fixed side electrode 122 in contact with the second thick plate 103. The current density in the energization path between 122 gradually decreases from the movable electrode 121 toward the fixed electrode 122, and the welding strength between the thin plate 101 and the thick plate 102 is improved.

  However, the movable electrode 121 is fixed to the movable electrode 121 according to the pressure applied by the movable electrode 121 and the fixed electrode 122, the thickness of the thin plate 101, the first thick plate 102, the second thick plate 103, and the shape and part of the member 100 to be welded. Various current densities in the energization path between the side electrodes 122 change, and it is difficult to ensure uniform welding quality. Further, various movable side electrodes 121 and fixed side electrodes 122 having different tip diameters depending on the thicknesses of the thin plate 101, the first thick plate 102, and the second thick plate 103 and the shape and part of the member to be welded 100 are replaced in various ways. The use is extremely troublesome, and there is concern about a significant decrease in productivity, which is not realistic. In addition, it requires a lot of management costs to prepare and manage various movable-side electrodes 121 and fixed-side electrodes 122 having different tip diameters.

  On the other hand, in Patent Document 2, the spot welding device 130 is moved to each spot position of the member to be welded 100 supported by the clamper 128, and the fixed electrode 134 is placed on the second thick plate 103 side of the member to be welded 100. The movable side electrode 135 is brought into contact with the thin plate 101 and the base portion 132 is further pushed up so that the pressure FU on the movable side 135 is smaller than the pressure FL on the fixed side 134. In addition, the current density between the thin plate 101 and the first thick plate 102 is increased, the amount of heat generated at the joint between the thin plate 101 and the first thick plate 102 can be secured, the amount of penetration is increased, and the welding strength is increased.

  However, the welding member 100 held by the clamper 128 is clamped and pressed by the fixed electrode 134 and the movable electrode 135, and the base portion 132 is moved to apply the pressure FL of the fixed electrode 134. In order to further reduce the pressure FU applied by the movable electrode 135, a large load is required for the clamper 128 that clamps and holds the member to be welded 100. On the other hand, in a state where the clamp position of the member 100 to be welded by the clamper 128 and the welding position, that is, the welding spot position, are separated, the member 100 to be welded is deformed and deformed by the applied pressure FL by the fixed side electrode 134 and the movable side electrode 135. It is difficult to ensure a stable contact resistance between the thin plate 101 and the first thick plate 102 and a contact resistance between the first thick plate 102 and the second thick plate 103 due to variations in the applied pressure FU. There is a concern that the current density at the joint of the welded member 100 varies and the quality of spot welding is degraded. Moreover, it cannot be used in a spot welding apparatus having an equalizing function between the wrist and base portion of the robot so that it can be moved by a reaction force during welding pressurization, and the spot welding apparatus is limited.

Therefore, purpose of the present invention was made in view of such a point, in the case of spot welding member to be welded of 4 ply on both surfaces of the two planks superimposed respectively superposed thin, uniform stable An object of the present invention is to provide a spot welding method and a spot welding apparatus that can achieve the weld quality.

Spot welding method according to the invention described in claim 1 to achieve the above Purpose is first sheet and second sheet, the first plank thickness is greater than the first sheet and the second sheet, the second plank In the spot welding method of spot welding a member to be welded in the order of the first thin plate, the first thick plate, the second thick plate, and the second thin plate, the first welding electrode contacting the second thin plate and the first The member to be welded is sandwiched and pressurized by a first control pressurizing portion that is in contact with the second thin plate adjacent to the welding electrode and a second welding electrode that is in contact with the first thin plate opposite to the first welding electrode. A first welding step in which spot welding is performed by energizing between the second welding electrode and the first welding electrode in the clamping pressure state, and a state in which a member to be welded is sandwiched by the first welding electrode and the second welding electrode While maintaining the first control pressure unit away from the second thin plate and the second A second control pressure member is brought into contact with the first thin plate adjacent to the contact electrode, and the member to be welded is clamped and pressed by the first welding electrode, the second welding electrode, and the second control pressure member. And a second welding step of spot welding by energizing between the second welding electrode and the first welding electrode.

  According to this, in a 1st welding process, a 1st welding is carried out by pinching and pressing a to-be-welded member with the 1st welding electrode and 1st control pressurizing part on the 2nd thin plate side, and the 2nd welding electrode on the 1st thin plate side. When the pressure applied to the second thin plate by the electrode is smaller than the pressure applied to the first thin plate by the second welding electrode, the second thin plate and the second thickness are applied when current is applied between the second welding electrode and the first welding electrode. The current density at the junction of the plates is relatively higher than the current density at the junction of the first thick plate and the first thin plate, and the amount of penetration between the second thin plate and the second thick plate increases. On the other hand, in the second welding step, the member to be welded is sandwiched and pressurized by the second welding electrode and the second control pressurizing unit on the first thin plate side and the first welding electrode on the second thin plate side. The applied pressure on the first thin plate side is smaller than the applied pressure on the second thin plate side by the first welding electrode, and when the first thin plate and the first thick plate are energized between the second welding electrode and the first welding electrode, The current density at the joint is relatively higher than the current density at the joint between the second thick plate and the second thin plate, and the amount of penetration between the first thin plate and the first thick plate is increased. A good nugget with no deviation in the amount of penetration is formed over the thin plate, and the welding quality for the member to be welded is improved.

The invention of claim 2 is the method of spot welding according to claim 1, the pressure applied by the first welding electrode to the second sheet in the clamping pressure state of the first welding FL, the first When the first control pressure applied to the second thin plate by the control pressurizing unit is Fα and the pressure applied to the first thin plate by the second welding electrode is FU, FU = FL + Fα, and the second welding. The applied pressure applied to the second thin plate by the first welding electrode in the clamping pressure state of the process is FL, the applied pressure applied to the first thin plate by the second welding electrode is FU, and the second controlled pressurization When the second control pressure applied to the first thin plate by the section is Fβ, FL = FU + Fβ.

  According to this, the sum total of the pressurizing force FL of the first welding electrode acting on the second thin plate side and the first control pressurizing force Fα of the first control pressurizing portion in the sandwich pressurizing state in the first welding step, and the second thin plate The applied pressure FU of the second welding electrode acting on the side becomes uniform (FU = FL + Fα), and the member to be welded is held in a stable state by the first welding electrode, the first control pressure unit, and the second welding electrode. In addition, the pressure applied by the first welding electrode on the second thin plate side can be made smaller than the pressure applied by the second welding electrode on the first thin plate side. In addition, the sum of the pressurizing force FU of the second welding electrode acting on the first thin plate side and the second control pressurizing force Fb by the second control pressurizing unit in the sandwiching pressurization state in the second welding step, and the first thin plate side The applied pressure FU of the acting second welding electrode becomes uniform (FL = FU + Fβ), and the member to be welded is held in a stable state by the first welding electrode, the second welding electrode, and the second control pressure unit. The pressure applied by the second welding electrode on the first thin plate side can be made smaller than the pressure applied by the first welding electrode on the second thin plate side.

Spot welding apparatus according to the invention described in claim 3 to achieve the above Purpose is first sheet and second sheet, the first plank thickness is greater than the first sheet and the second sheet, the second plank In the spot welding apparatus for spot welding a member to be welded in which the first thin plate, the first thick plate, the second thick plate, and the second thin plate are stacked in the plate order, the first welding electrode facing the second thin plate, A second welding electrode which is coaxial with the first welding electrode and opposes the first thin plate of the welding member to clamp and press the member to be welded in cooperation with the first welding electrode; and adjacent to the first welding electrode A first control pressurizing unit that applies a first control pressure to the second thin plate, and a second control pressurization unit that applies a second control pressurization to the first thin plate adjacent to the second welding electrode; A first welding electrode that contacts the second thin plate, a first control pressure unit, and the first welding electrode. And sandwiching and pressurizing the member to be welded by the second welding electrode in contact with the first thin plate, energizing and spot welding between the second welding electrode and the first welding electrode in the sandwiching and pressing state, The member to be welded is sandwiched and pressurized by a first welding electrode that contacts the second thin plate, a second welding electrode that faces the first welding electrode and contacts the first thin plate, and a second control pressure unit. Spot welding is performed by energizing the second welding electrode and the first welding electrode in a pressurized state.

  According to this, in a 1st welding process, a 1st welding is carried out by pinching and pressing a to-be-welded member with the 1st welding electrode and 1st control pressurizing part on the 2nd thin plate side, and the 2nd welding electrode on the 1st thin plate side. The applied pressure on the second thin plate side by the electrode is smaller than the applied pressure on the first thin plate side by the second welding electrode, and when the second welding electrode and the first welding electrode are energized, the second thin plate and the second thick plate The current density at the contact location is relatively higher than the current density at the contact location between the first thick plate and the first thin plate, the amount of penetration of the second thin plate and the second thick plate is increased, and the welding strength is secured. In the two-welding process, the first thin plate by the second welding electrode is formed by sandwiching and pressing the member to be welded by the second welding electrode and the second control pressure unit on the first thin plate side and the first welding electrode on the second thin plate side. Side pressure is greater than the pressure applied to the second thin plate by the first welding electrode When the second welding electrode and the first welding electrode are energized, the current density at the contact point between the first thin plate and the first thick plate is smaller than the current density at the contact point between the second thick plate and the second thin plate. It becomes relatively high, the amount of penetration of the first thin plate and the second thick plate is increased, the welding strength is ensured, and there is no unevenness from the first thin plate to the second thin plate and from the first thin plate to the second thin plate. A nugget is formed, and the welding quality for the member to be welded is improved.

Spot welding apparatus according to the invention described in claim 4 to achieve the above Purpose is first sheet and second sheet, the first plank thickness is greater than the first sheet and the second sheet, the second plank , A spot welding apparatus for spot welding a member to be welded that is superposed in order of a first thin plate, a first thick plate, a second thick plate, and a second thin plate, and a base portion and a second thick plate supported by the base portion A first welding electrode that contacts, and a second welding electrode that is mounted on the base portion and supports a second welding electrode via a rod, and that cooperates with the first welding electrode by contacting the second welding electrode to the first thin plate A pressure actuator that moves between a pressurizing position that sandwiches the member to be welded and applies pressure to the member to be welded and a retracted position that is separated from the member to be welded, and the first welding electrode of the member to be welded A first control pressure is applied to the second thin plate adjacent to the first thin plate. And a control pressure applying means having a second control pressurizing unit for applying a second control pressure to the first thin plate adjacent to the second welding electrode of the member to be welded, and against the second thin plate The member to be welded is sandwiched and pressurized by the first welding electrode and the first control pressurizing unit that are in contact with each other and the second welding electrode that is opposed to the first welding electrode and is in contact with the first thin plate. A first welding electrode that is energized and spot-welded between the second welding electrode and the first welding electrode, abuts against the second thin plate, and a second welding that abuts the first thin plate opposite the first welding electrode. The member to be welded is sandwiched and pressurized by an electrode and a second control pressurizing unit, and spot welding is performed by energizing between the second welding electrode and the first welding electrode in the sandwiched and pressurized state. .

  According to this, the first welding electrode that contacts the second thin plate, the first control pressure unit that contacts the second thin plate adjacent to the first welding electrode, and the first thin plate facing the second welding electrode. By sandwiching and pressurizing the member to be welded by the second welding electrode that is in contact, the pressure applied by the pressure actuator is applied from the second welding electrode to the first thin plate and from the first welding electrode to the second thin plate via the base portion. Further, a first control pressure applied by the first control pressurizing unit is applied to the second thin plate, and a pressure on the second thin plate side by the first welding electrode is applied to the first thin plate side by the second welding electrode. Smaller.

  Thereby, when it supplies with electricity between this 2nd welding electrode and the 1st welding electrode, the current density between the 2nd thin plate and the 2nd thick plate becomes large, and it melts from the 2nd thin plate to the 2nd thick plate. A good nugget with no amount bias is formed. Further, a second welding electrode that contacts the first thin plate, a second control pressure unit that contacts the first thin plate adjacent to the second welding electrode, and a second contact that contacts the second thin plate facing the second welding electrode. By sandwiching and pressurizing the member to be welded with one welding electrode, the second control pressing force by the second control pressing unit is applied to the first thin plate, and the first thin plate side pressing force by the second welding electrode is the first. It becomes smaller than the applied pressure on the second thin plate side by the welding electrode. Thereby, when it supplies with electricity between this 2nd welding electrode and the 1st welding electrode, the current density between the 1st thin plate and the 1st thick plate becomes large, and it melts from the 1st thin plate to the 1st thick plate. A good nugget with no unevenness of the amount is formed, and the welding quality for the member to be welded is improved.

  Here, the control pressure application means is mounted on the first control pressure unit and the second control pressure unit and the base unit to support the first control pressure unit and the second control pressure unit, and A first pressure applying position in which the first control pressurizing unit abuts on the second thin plate adjacent to the first welding electrode to apply the first control pressurizing force and the second control pressurizing unit is separated from the first thin plate. And the first control pressurizing unit is separated from the second thin plate, and the second control pressurizing unit is in contact with the first thin plate adjacent to the second welding electrode and applies the second control pressurizing force. It can be constituted by a controlled pressure actuator that is selectively moved to the application position.

According to the present invention, the first thin plate, the second thin plate, and the first thick plate and the second thick plate having a thickness greater than that of the first thin plate and the second thin plate, the first thin plate, the first thick plate, and the second thick plate. When spot welding a four-layer member to be welded in the order of the second thin plate, the first welding electrode on the second thin plate side, the first control pressure unit, and the second welding electrode on the first thin plate side are covered. By sandwiching and pressurizing the welding member, the contact pressure between the second thin plate and the second thick plate is smaller than the contact pressure between the first thick plate and the first thin plate in the sandwiching and pressurizing portion formed by the first welding electrode and the second welding electrode. The current density at the joint between the second thin plate and the second thick plate is greater than the current density at the joint between the first thick plate and the first thin plate when energized between the second welding electrode and the first welding electrode. The welding strength of the second thin plate and the second thick plate is secured, and the second welding current on the first thin plate side is further increased. And the second control pressure unit and the first welding electrode on the second thin plate side sandwich and press the member to be welded, so that the first thin plate and the first thickness are sandwiched and pressurized by the second welding electrode and the first welding electrode. The contact pressure between the plates becomes smaller than the contact pressure between the second thick plate and the second thin plate, and the current density at the contact point between the first thin plate and the first thick plate when the second welding electrode and the first welding electrode are energized. Is relatively increased with respect to the current density at the contact point between the second thick plate and the second thin plate, the welding strength of the first thin plate and the first thick plate is ensured, and the first thin plate extends from the second thin plate to the first thin plate. A good nugget with no bias is formed from the thin plate to the second thin plate, and the welding quality for the member to be welded is improved.

It is a block diagram of the spot welding apparatus in a 1st reference example . It is a principal part expansion perspective view. It is a spot welding apparatus operation | movement process drawing. It is an operation explanatory view. It is operation | movement explanatory drawing of a comparative example. It is a spot welding apparatus operation | movement process drawing. It is an operation explanatory view. It is a figure which shows the example of expansion | deployment of a to-be-welded member. It is a figure which shows the outline | summary of the 2nd reference example . It is a principal part expansion perspective view. It is a spot welding apparatus operation | movement process drawing. It is a block diagram of a spot welding apparatus in the form of implementation. It is a principal part expansion perspective view. It is a spot welding apparatus operation | movement process drawing. It is an operation explanatory view. It is an operation explanatory view. It is a figure which shows the example of expansion | deployment of a to-be-welded member. It is explanatory drawing which shows the outline | summary of the conventional spot welding. It is explanatory drawing which shows the outline | summary of the conventional spot welding. It is explanatory drawing which shows the outline | summary of the conventional spot welding. It is explanatory drawing which shows the outline | summary of the conventional spot welding.

(First Reference Example )
Hereinafter, a first reference example of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of a spot welding apparatus, and FIG. 2 is an explanatory view of a main part of the spot welding apparatus.

  In FIG. 1, 1 is a welding robot, 10 is a spot welding apparatus supported by the welding robot 1, and 100 is a member to be welded.

  Prior to the description of the welding robot 1 and the spot welding apparatus 10, the welded member 100 will be described. The member to be welded 100 is obtained by superimposing a thin plate on one of two stacked thick plates, for example, a thin plate 101 having a lower rigidity in order from the top, a first thick plate 102 having a thickness greater than that of the thin plate 101 and a higher rigidity. It is constituted by a three-layered plate set in which two thick plates 103 are overlapped.

  The welding robot 1 is, for example, an articulated robot, and has a base fixed to a floor (not shown), a plurality of arms 2 and a wrist 3 attached to the tip of the arm 2, and an equalizer unit 4 is interposed in the wrist 3. The spot welding apparatus 10 supported in this manner is configured to be movable in a three-dimensional direction. The equalizer unit 4 is interposed between the spot welding device 10 and the wrist 3 and supports the spot welding device 10 on the arm 2 so as to be movable by the reaction force when the member 100 to be welded is pressed by the spot welding device 10.

  Then, the welding robot 1 sequentially moves the spot welding device 10 to each preset spot position of the welded member 100 held at a predetermined position by a clamper or the like (not shown), that is, a welded portion, to the welded member 100. Perform spot welding.

  The spot welding apparatus 10 includes a base portion 11 that is attached to the wrist portion 3 via the equalizer unit 4. A C-shaped yoke 13 that extends downward is attached to the base portion 11, and a fixed-side electrode 14 that is a first welding electrode is attached to the lower end tip of the C-shaped yoke 13.

  In addition, a pressure actuator 15 using a cylinder device or a servo motor as a driving source in the present embodiment is mounted on the upper end of the base portion 11. A rod 16 that moves forward and backward along the axis of the fixed side electrode 14 in a direction to come in contact with and away from the fixed side electrode 14 by the operation of the pressurizing actuator 15 projects below the base portion 11, and the fixed side electrode is formed at the tip of the rod 16. A movable electrode 17 is attached as a second welding electrode that is disposed opposite to the movable electrode 14 and can move forward and backward on the same axis as the fixed electrode 14. As a result, the movable side electrode 17 moves closer to the retraction position of the ascending moving end separated from the fixed side electrode 14 by the operation of the pressurizing actuator 15 and the fixed side electrode 14, so that the member 100 to be welded cooperates with the fixed side electrode 14. Then, it is clamped, that is, clamped and moved toward and away from the fixed electrode 14 between the pressurizing position for applying pressure to the member 100 to be welded.

  In addition, the base portion 11 is adjacent to the position adjacent to the movable electrode 17, that is, the welding position, to the thin plate 101 of the member to be welded 100 that is sandwiched and pressed by the fixed electrode 14 and the movable electrode 17. Control pressure applying means 20 for applying a control pressure to the position is provided.

  As shown in FIGS. 1 and 2, the control pressure applying means 20 separates the rod 16 as shown in an enlarged perspective view of the main part, and has base ends attached to both sides of the base portion 11 on the C-shaped yoke 13 side. Air cylinders 21 and 23, which are a pair of control pressure actuators extending in parallel with the advance and retreat directions, are provided. Each air cylinder 21, 23 selectively supplies air from the air supply source 31 to the expansion side air chamber or the contraction side air chamber via the air supply switching valve 32, so The protruding cylinder rods 22 and 24 extend and retract, and the cylinder rods 22 and 24 are held at the positions by holding air in the contraction-side air chamber or the extension-side air chamber.

  A connecting plate 25 is stretched between the tips 22a and 24a of the cylinder rods 22 and 24 protruding from the tips of the air cylinders 21 and 23. A band-like shape in which the base end portion is coupled between the center portion of the connecting plate 25, that is, the tip ends 22a and 24a of the cylinder rods 22 and 24 in the connecting plate 25, and the tip end portion extends away from the C-shaped yoke 13 side. A member-to-be-welded member 26 is provided. An electrode insertion portion 27 that is cut out in an arc shape or a concave shape into which the movable side electrode 17 and the fixed side electrode 14 can be inserted is formed at the distal end portion of the member to be welded 26, and on both sides of the electrode insertion portion 27. A pair of protruding restricting portions 28 and 29 is formed. Protruding restricting surface pieces 28a and 29a whose tops protrude in a hemispherical shape as control pressurizing portions are provided on the lower surfaces of the restricting portions 28 and 29, respectively. Restricting surface pieces 28b and 29b are provided. The regulating surface pieces 28 a and 29 a and 28 b and 29 b are preferably provided at symmetrical positions adjacent to the axis of the movable electrode 17 and centered on the axis of the movable electrode 17.

Further, the air cylinders 21 and 23 include a first retraction position detection sensor S1 that detects a first retraction position in which the cylinder rods 22 and 24 of the air cylinders 21 and 23 are contracted and become an upward movement end, a fixed electrode 14, and the like. First pressurization for detecting a first pressurization position that is an extension position of the air cylinders 21 and 23 in a state in which the regulating surface pieces 28a and 29a are pressed from above onto the upper surface of the member 100 to be welded sandwiched by the movable electrode 17. The position detection sensor S2, the second retraction position detection sensor S3 for detecting the second retraction position where the cylinder rods 22 and 24 of the air cylinders 21 and 23 are extended and become the descending movement end, and the fixed side electrode 14 and the movable side electrode 17 Position of the air cylinders 21 and 23 in a state where the regulating surface pieces 28b and 29b are pressed against the lower surface of the member 100 to be welded sandwiched by A second pressing position sensor S4 for detecting a certain second pressure position.

The welding robot controller RC stores teaching data of the welding robot 1. In the teaching data, an operation program for sequentially spot-welding each welding spot of the member to be welded 100 and each welding spot, that is, a welding position, are spot-welded. The position and posture of the spot welding apparatus 10 when performing are included. Further, the welding device controller operation program and the first retreat avoid position detection sensor S1 of the WC spot welding apparatus 10, a first pressing position detection sensor S2, the second retraction position detection sensor S3, a second pressing position detection sensor S4 The operation control of the air supply switching valve 32 based on this detection is included.

  For example, when the first retraction position detection sensor S1 detects that the air cylinders 21 and 23 are supplied from the extended state to the contraction-side air chamber and the air cylinders 21 and 23 contract to reach the first retraction position. Based on the detection signal, the air supply switching valve 32 is switched to the first retracted position, the air supply to each contraction-side air chamber is stopped, and the air is held in the contraction-side air chamber so that the air cylinders 21, 23 are in the first position. 1 held in the retracted position.

  The air supply switching valve 32 is switched from the first retracted position to discharge the air in the contraction-side air chamber, and the air cylinders 21 and 23 that are extended by supplying air to the extension-side air chamber are in the first pressure position. When the first pressurization position detection sensor S2 detects that the air pressure has reached, the air supply switching valve 32 is switched to the first pressurization position based on the detection signal, and the air supply into each extension side air chamber is stopped. Air is held in the extension-side air chamber, and the air cylinders 21 and 23 are held at the first pressurizing position.

When the second retreat avoid position detection sensor S3 that the air cylinder 21 and 23 the air cylinders 21 and 23 is air is supplied to the decompression side air chamber has reached the second retracted position by expanding detects, the detection Based on the signal, the air supply switching valve 32 is switched to the second retracted position, the air supply to each extension side air chamber is stopped, the air in the extension side air chamber is held, and the air cylinders 21 and 23 are second retracted. Held in position. The air supply switching valve 32 is switched from the second retracted position so that the air in the expansion side air chamber is discharged and the air cylinders 21 and 23 that are contracted by supplying air to the contraction side air chamber reach the second pressurization position. When the second pressurization position detection sensor S2 detects this, the air supply switching valve 32 is switched to the second pressurization position based on the detection signal, and the air supply to each contraction side air chamber stops and contracts. The air in the side air chamber is held, and the air cylinders 21 and 23 are held at the second pressurizing position.

  Next, the operation of the spot welding apparatus 10 will be described. In this description, for convenience of explanation, a case in which a member 100 to be welded by spot welding is constituted by a three-layered plate set in which a thin plate 101, a first thick plate 102, and a second thick plate 103 are stacked in order from the top. 3, the operation explanatory diagram shown in FIG. 4, and the operation explanatory diagram of the comparative example shown in FIG. 5, followed by the member 100 to be welded in order from the bottom, the thin plate 101, the first A case in which the thick plate 102 and the second thick plate 103 are configured by a three-layered plate set will be described with reference to the spot welding apparatus operation process diagram shown in FIG. 6 and the operation explanatory diagram shown in FIG.

In spot welding of the member to be welded 100 in which the thin plate 101, the first thick plate 102, and the second thick plate 103 are superposed in order from the top, the movable electrode 17 as shown in FIG. 3 (a) according to a preset operation program. Is in a retracted position away from the fixed side electrode 14 and the member to be welded 26 of the control pressurizing application means 20 is held in the vicinity of the movable side electrode 17, that is, the air cylinders 21 and 23 are extended to perform the first retraction. When it is confirmed that the position detection sensor S1 has not detected the first retracted position of the air cylinders 21, 23, that is, the position of the member to be welded 26 is confirmed, the air supply switching valve is operated by an operation signal from the welding apparatus controller WC. 32 is switched to start air supply into the contraction-side air chamber of the air cylinders 21 and 23, and the air cylinders 21 and 23 contract. As the air cylinders 21 and 23 contract, the welded member holder 26 is pulled up above the tip of the movable electrode 17. Then, and FIG. 3 (b) is an air cylinder 21, 23 contracts as shown in reaching the first retreat avoid position detection sensor S1 detects the first retracted position, switching the air feed switching valve 32 is in the first retracted position Thus, the air supply to the contraction-side air chamber of the air cylinders 21 and 23 is stopped, and the air is held in the contraction-side air chamber. Thereby, the to-be-welded member press 26 is held at the first retracted position.

Next, the air cylinder 21, 23 when it is first retracted position is confirmed by the detection signal of the first retreat avoid position detection sensor S1, a welding robot controller RC operates the welding robot 1 is set in advance The spot welding apparatus 10 is moved to the spot position of the member to be welded 100 according to the program, and the welded portion of the member to be welded 100 is fixed to the fixed electrode 14, the movable electrode 17, and the regulating surface piece 28a as shown in FIG. , 28a, and the fixed-side electrode 14 is positioned in contact with the specified position of the second thick plate 103 corresponding to the hit position.

  In a state where the spot welding apparatus 10 is positioned at the welding position, the tip of the fixed electrode 24 comes into contact with the second thick plate 103 of the contact welding member 100 from below as shown in FIG. The tip of the side electrode 17 and the regulating surface pieces 28a and 29a face the thin plate 101 with a gap.

  Next, as shown in FIG. 3D, the movable side electrode 17 is fixed from the retracted position by the operation of the pressure actuator 15 in a state where the fixed side electrode 14 is in contact with the second thick plate 103 of the member to be welded 100. It moves in the direction of the pressurizing position approaching the side electrode 14 and is brought into pressure contact with the thin plate 101. As a result, the pressurizing force of the pressure actuator 15 acts on the movable electrode 17 via the movable electrode 14 and the base 11, and the welded member 100 is welded between the movable electrode 17 and the fixed electrode 14. The part is sandwiched and pressurized.

  On the other hand, the air supply switching valve 32 is switched to discharge the air in the contraction-side air chamber of the air cylinders 21 and 23, and the air is supplied to the extension-side air chamber to extend the air cylinders 21 and 23 to hold the welded member. 26 is lowered, and the regulating surface pieces 28a and 29a are pressed against the thin plate 101 of the member to be welded 100 from above and adjacent to the movable electrode 17, and the air cylinders 21 and 23 that extend further reach the first pressure position. The first pressurization position detection sensor S2 detects, the air supply switching valve 32 is switched to the first pressurization position to stop the air supply to the extension side air chamber of the air cylinders 21, 23, and the extension side air chamber Keep air in the air. Thereby, the to-be-welded member holding | suppressing 26 is hold | maintained in a 1st pressurization position.

  In this way, the member to be welded 100 is sandwiched and pressed by the fixed side electrode 14 and the pressure side electrode 17, and the thin plate 101 is pressed by the air cylinders 21 and 23 adjacent to the movable side electrode 17 by the regulating surface pieces 28 a and 29 a. In this state, as shown schematically in FIG. 4, an operation explanatory diagram is schematically applied to the second thick plate 103 of the member to be welded 100 from the lower side, and a pressure FU applied by the movable electrode 17. The control pressure Fα by the regulating surface pieces 28 a and 29 a by the air cylinders 21 and 23 is applied to the thin plate 101 adjacent to the movable electrode 17.

  In this case, the pressurizing force of the pressurizing actuator 15 and the control pressurizing force of the air cylinders 21 and 23 act on the fixed side electrode 14 via the movable side electrode 17 and the regulating surface pieces 28a and 29a, the base portion 11 and the C-shaped yoke 13. The sum of the pressing force FL by the fixed electrode 14 acting on the second thick plate 103 is equal to the pressing force FU by the movable electrode 17 acting on the thin plate 101 and the control pressing force Fα by the regulating surface pieces 28a and 29a. (FL = FU + Fα).

  As a result, the member to be welded 100 has a pressing force FL from the fixed side electrode 14 acting on the second thick plate 103 side from below and a pressing force FU and a regulating surface from the movable side electrode 17 acting on the thin plate 101 side from above. It is held and held in a stable state by the control pressure Fα from the pieces 28a and 29a.

  On the other hand, a pressing force FL is applied to the second thick plate 103 from the fixed electrode 14 to the welded part of the member 100 to be welded, and from the pressing force FL by the fixed electrode 14 as a pressing force FU from the movable electrode 17 to the thin plate 101. A pressing force having a magnitude obtained by subtracting the control pressing force Fα by the regulating surface pieces 28a and 29a is applied (FU = FL−Fα).

  The pressing force FU of the movable side electrode 17 positioned on the thin plate 101 side is made smaller than the pressing force FL of the fixed side electrode 14 positioned on the second thick plate 103 side (FU <FL). The contact pressure at the joint of the plate 102 is smaller than the contact pressure at the joint between the first thick plate 102 and the second thick plate 103, and the contact resistance between the thin plate 101 and the first thick plate 102 is relatively high. The contact resistance between the first thick plate 102 and the second thick plate 103 decreases as the size increases.

  Here, for example, the movable side electrode 17 is actuated by the operation of the pressure actuator 15 in a state where the fixed side electrode 14 is in contact with the second thick plate 103 of the member 100 to be welded by the spot welding apparatus 10 that does not include the control pressure applying means 20. Is pressed against the thin plate 101 to sandwich the welded portion of the welded member 100 between the fixed side electrode 14 and the movable side electrode 17 and is applied with pressure, as shown schematically in FIG. The applied pressure of the pressure actuator 15 acts equally on the fixed side electrode 14 via the movable side electrode 17, the base portion 11 and the C-shaped yoke 13, and the applied pressure FL applied to the second thick plate 103 by the fixed electrode 14. A pressure FL applied to the thin plate 101 by the movable side electrode 17 is applied.

  Next, the member 100 to be welded is sandwiched and applied by the fixed side electrode 14 and the movable side electrode 17, and the control pressing force is applied by the regulating surface pieces 28 a and 29 a, so that the movable side electrode 17 positioned on the thin plate 101 side is applied. In a state where the applied pressure FU is smaller than the applied pressure FL of the fixed side electrode 14 located on the second thick plate 103 side, a predetermined time is provided between the movable side electrode 17 and the fixed side electrode 14 as shown in FIG. Energize and weld. When the movable side electrode 17 and the fixed side electrode 14 are energized, the contact resistance between the thin plate 101 and the first thick plate 102 is relatively large and the current density is increased. The contact resistance between 102 and the second thick plate 103 is kept small. As a result, the amount of heat generated at the joint between the thin plate 101 and the first thick plate 102 is relatively increased with respect to the amount of heat generated at the joint between the first thick plate 102 and the second thick plate 103, and the second from the thin plate 101. A good nugget with no uneven current density is formed over the thick plate 103, and the welding strength of the thin plate 101 can be ensured.

After this welding is completed, the movable electrode 17 is moved from the pressurization position to the retracted position by the operation of the pressurizing actuator 15 to release the member 100 to be welded between the fixed electrode 14 and the movable electrode 17. On the other hand, the air cylinder supply switching valve 32 is switched to discharge air in the expansion side air chamber of the air cylinders 21 and 23 and supply air to the contraction side air chamber to contract the air cylinders 21 and 23. As the air cylinders 21 and 23 contract, the welded member holder 26 is pulled up above the tip of the movable electrode 17. Then, 3 air cylinders 21 and 23 to contract, as shown in (f) reaches the detected first retreat avoid position detection sensor S1 is in the first retracted position, switching the air feed switching valve 32 is in the first retracted position Thus, the air supply to the contraction-side air chamber of the air cylinders 21 and 23 is stopped, and the air is held in the contraction-side air chamber. Thereby, the to-be-welded member press 26 is held at the first retracted position.

Next, when that the air cylinder 21 and 23 is first retracted position is confirmed to the detection signal of the first retreat avoid position detection sensor S1, the welding robot 1 operates as shown in FIG. 3 (g) Then, the spot welding apparatus 10 is retracted from the member to be welded 100 and moved to the hit position of the next member to be welded 100.

  Next, a case where the member to be welded 100 is constituted by a three-layered plate assembly in which the thin plate 101, the first thick plate 102, and the second thick plate 103 are overlapped in order from the bottom is shown in FIG. The operation will be described with reference to FIGS.

In spot welding of the member to be welded 100 in which the thin plate 101, the first thick plate 102, and the second thick plate 103 are stacked in order from the bottom, the movable side electrode 17 is shown in FIG. 6A according to a preset operation program. There state in which the welding member retainer 26 of the fixed-side electrode 14 retracted position and controllable pressure applying means 20 has moved away from being held in the vicinity of the movable side electrode 17, i.e. the second retreat avoid position detection sensor S3 is an air cylinder 21 , 23 is not detected, the air supply switching valve 32 is switched to start supplying air into the expansion side air chamber of the air cylinders 21, 23, and the air cylinders 21, 23 are switched. Stretches.

  As the air cylinders 21 and 23 extend, the welded member holder 26 descends below the tip of the fixed electrode 14. Then, as shown in FIG. 6 (b), the second retracted position detection sensor S3 detects that the air cylinders 21 and 23 extending have reached the second retracted position, and the air supply switching valve 32 is moved to the second retracted position. The air supply to the extension side air chamber of the air cylinders 21 and 23 is stopped by switching, and the air is held in the extension side air chamber. Thereby, the to-be-welded member press 26 is held at the second retracted position.

  Next, when it is confirmed by the detection signal of the second retracted position detection sensor S3 that the air cylinders 21 and 23 are in the second retracted position, the welding robot 1 is operated to perform spot welding according to a preset program. 10 is moved to the spot position of the member to be welded 100, and the welded portion of the member to be welded 100 is positioned between the fixed side electrode 14, the movable side electrode 17, and the regulating surface pieces 28b and 29b as shown in FIG. In addition, the fixed side electrode 14 is positioned so as to be in contact with the specified position of the thin plate 101 corresponding to the hit position.

  In a state where the spot welding apparatus 10 is positioned at the welding position, as shown in FIG. 6C, the tip of the fixed side electrode 14 comes into contact with the thin plate 101 of the welded member 100 from below, while the movable side electrode 17 The front end faces the second thick plate 103 with a gap, and the regulation surface pieces 28b and 29b face the thin plate 101 with a gap.

  Next, as shown in FIG. 6 (d), the movable side electrode 17 is moved from the retracted position to the pressurized position by the operation of the pressure actuator 15 with the fixed side electrode 14 in contact with the thin plate 101 of the member to be welded 100. The welded portion of the member to be welded 100 is sandwiched between the fixed-side electrode 14 and the movable-side electrode 17 and pressed.

  On the other hand, the air supply switching valve 32 is switched to discharge the air in the expansion side air chamber of the air cylinders 21 and 23, and the air is supplied to the contraction side air chamber and the air cylinders 21 and 23 are contracted to hold the welded member. 26 rises, the regulating surface pieces 28b and 29b are pressed against the thin plate 101 of the member to be welded 100 adjacent to the fixed side electrode 14 from below, and the air cylinders 21 and 23 that further contract reach the second pressurizing position. The second pressurization position detection sensor S4 detects, the air supply switching valve 32 is switched to the second pressurization position, and the air supply to the contraction side air chamber of the air cylinders 21, 23 is stopped, and the contraction side air chamber is stopped. Keep air in the air. Thereby, the to-be-welded member holding | suppressing 26 is hold | maintained in a 2nd pressurization position.

  In a state where the member to be welded 100 is sandwiched and pressurized by the fixed side electrode 14 and the movable side electrode 17 and the control surface pressure is applied to the thin plate 101 by the regulating surface pieces 28b and 29b by the air cylinders 21 and 23, FIG. As shown schematically in FIG. 1, a pressure FU applied by the movable electrode 17 is applied to the second thick plate 103 of the welded member 100 from above, and the pressure FL applied by the fixed electrode 14 and the air cylinders 21, 23 are applied. The control pressure Fα by the regulating surface pieces 28b and 29b is applied to the thin plate 101 from below.

  In this case, the pressurizing force of the pressurizing actuator 15 acts on the fixed electrode 14 via the movable electrode 17, the base portion 11, and the C-shaped yoke 13, and the control pressurizing force of the air cylinders 21, 23 is the regulating surface piece 28 b, 29 b and the base portion 11 acting on the movable side electrode 17, the pressure FU by the movable side electrode 17 acting on the second thick plate 103, the pressure FL by the fixed side electrode 14 acting on the thin plate 101, and the regulating surface piece The sum of the pressures Fα by 28b and 29b becomes equal (FU = FL + Fα). Thereby, the member 100 to be welded is held in a stable state by the fixed side electrode 14, the movable side electrode 17, and the regulating surface pieces 28b and 29b.

  On the other hand, a pressure FU is applied from the movable electrode 17 to the second thick plate 103 to the welded part of the member 100 to be welded, and a pressure FL from the fixed electrode 14 to the thin plate 101, that is, a pressure FU by the movable electrode 17. From the control surface pieces 28b and 29b, the applied pressure is reduced (FL = FU−Fα).

  The pressing force FL of the fixed electrode 14 positioned on the thin plate 101 side is made smaller than the pressing force FU of the movable electrode 17 positioned on the second thick plate 103 side (FL <FU), so that the thin plate 101 and the first thickness The contact pressure at the joint of the plate 102 is smaller than the contact pressure between the first thick plate 102 and the second thick plate 103, and the contact resistance between the thin plate 101 and the first thick plate 102 is relatively increased. The contact resistance between the first thick plate 102 and the second thick plate 103 is reduced.

  In a state where the member to be welded 100 is clamped and applied by the fixed side electrode 14 and the movable side electrode 17 and the control pressure Fα is applied by the regulating surface pieces 28b and 29b, the movable side electrode as shown in FIG. 17 and the fixed electrode 14 are energized for a predetermined time and welded. When the movable side electrode 17 and the fixed side electrode 14 are energized, the contact resistance of the joint between the thin plate 101 and the first thick plate 102 becomes relatively large, the current density becomes high, and the first thick plate Since the contact resistance between the first thick plate 102 and the second thick plate 103 is reduced, the amount of heat generated between the thin plate 101 and the first thick plate 102 is smaller than the amount of heat generated between the first thick plate 102 and the second thick plate 103. Increase relatively. Therefore, the amount of penetration from the thin plate 101 to the second thick plate 103 is ensured, and a good nugget N with no bias is formed, so that the welding strength of the thin plate 101 can be ensured.

After this welding is completed, as shown in FIG. 6 (f), the movable side electrode 17 is moved from the pressure position to the retracted position by the operation of the pressure actuator 15, and the fixed side electrode 14 and the movable side electrode 17 are used. The clamping of the member to be welded 100 is released. On the other hand, the air cylinder supply switching valve 32 is switched to discharge air in the contraction side air chamber of the air cylinders 21 and 23 and supply air to the extension side air chamber to extend the air cylinders 21 and 23. As the air cylinders 21 and 23 are extended, the member to be welded 26 is lowered below the tip of the fixed electrode 14. Then, the detected second when retracted reaches the position second retreat avoid position detecting sensor S3 by the air cylinder 21, 23 stretched as shown in FIG. 6 (f), the air supply switching valve 32 and the second retracted position By switching, the air supply to the extension side air chamber of the air cylinders 21 and 23 is stopped, and the air is held in the extension side air chamber. Thereby, the to-be-welded member press 26 is held at the second retracted position.

Next, when that the air cylinder 21 and 23 is in the second retracted position is confirmed to the detection signal of the second retreat avoid position detection sensor S3, the welding robot 1 operates as shown in FIG. 6 (g) Then, the spot welding apparatus 10 is retracted from the spot position of the welded member 100 and moved to the spot position of the next welded member 100.

  According to the present embodiment configured as described above, the thin plate 101 having a low rigidity, the first thick plate 102 having a higher rigidity than the thin plate 101, and the second thick plate 103 are combined to form a three-layered plate set. The spot welding apparatus 10 for spot welding the welded member 100 is fixed to the fixed side electrode 14 by the fixed side electrode 14 provided on the base part 11 via the C-shaped yoke 13 and the pressure actuator 15 provided on the base part 11. 14 and a control pressure applying means 20 for applying a control pressure to the vicinity of the welding position in the thin plate 101 of the member 100 to be welded and pressed by the fixed side electrode 14 and the movable side electrode 17. , A pressing force FL is applied by the fixed electrode 14, a pressing force FU is applied by the movable electrode 17, and a control pressing force is applied in the vicinity of the welding position of the welded member 100. By applying α, the contact pressure between the thin plate 101 and the first thick plate 102 is controlled to be smaller than the contact pressure between the first thick plate 102 and the second thick plate 103, and the movable side electrode 17 and the fixed side electrode 14 are energized. In this case, the current density at the junction between the thin plate 101 and the first thick plate 102 is relatively higher than the current density at the junction between the first thick plate 102 and the second thick plate 103. A good nugget with no unevenness which melted greatly over the thick plate 103 is formed, and the welding strength of the thin plate 101 can be ensured. In particular, the fixed side electrode 14 and the movable side electrode 17 are sandwiched and pressurized to apply the pressure FL by the fixed side electrode 14 and the pressure FU by the movable side electrode 17. Since the pressure Fα is applied, a good nugget without bias is formed from the thin plate 101 to the second thick plate 103 at various welding positions without being affected by the clamping position for clamping the member to be welded 100, Welding quality can be secured.

In the above reference example , the case where the air cylinders 21 and 23 are used as the control pressure actuators has been described as an example.

  Moreover, although the case where it formed by the protruding regulation surface piece 28a, 29a, 28b, 29b as a control pressurizing part was demonstrated to the example, it can change variously according to the shape etc. of the to-be-welded member 100. For example, as shown in FIG. 8 corresponding to FIG. 2, it is projected on a connecting plate 25 spanned between the tips 22 a and 24 a of the cylinder rods 22 and 24 that protrude from the tips of the air cylinders 21 and 23. A semicircular arc shape that protrudes along the electrode insertion portion 27 on the lower surface of the regulation portions 28 and 29 formed along the electrode insertion portion 27 that is cut out in an arc shape or a concave shape at the distal end portion of the pressed member 26 to be welded. The regulating surface piece 28A and the regulating portions 28 and 29 can be formed by a semicircular arc shaped regulating surface piece 28B protruding along the electrode insertion portion 27.

(Second reference example )
Hereinafter, a second reference example of the present invention will be described with reference to FIGS. FIG. 9 is a configuration diagram of the spot welding apparatus, and FIG. 10 is an enlarged explanatory view of a main part of the spot welding apparatus. FIG. 11 is an explanatory diagram of the operation. 9 to 11, the same reference numerals are assigned to the portions corresponding to those in FIGS. 1 and 2, and the detailed description thereof is omitted.

The spot welding apparatus 40 of the present reference example is configured by a control pressure applying unit 41 supported by the rod 16 instead of the control pressure applying unit 20 of the first reference example .

  As shown in FIGS. 9 and 10, the rod 16 of the spot welding apparatus 40 is a columnar shape in which a base end portion 16A protruding downward from the base portion 11 is formed with a relatively large diameter, and the tip end of the base end portion 16A. A shaft portion 16C formed in a cylindrical shape with a smaller diameter than the base end portion 16A is coaxially formed on the side through the step portion 16B, and the movable side electrode 17 is provided on the shank portion 16D formed at the tip of the shaft portion 16C. Installed. The shaft portion 16 </ b> C is formed with a larger diameter than the movable side electrode 17.

The control pressurizing application means 41 is constituted by a cylindrical elastic member having an insulation coating process that can be fitted to the shaft portion 16C, which is a coil spring 42 in this reference example .

  The coil spring 42 has a base end 42a abutting against the stepped portion 16B, a base end portion 42b fitted to the tip end portion 16C and mounted on the rod 16, and a tip end portion 42c serving as a control pressurizing portion in a no-load state is movable. It has an effective length protruding from the tip of the side electrode 17.

  Thus, in the spot welding apparatus 40 provided with the control pressure applying means 41, the movable side electrode 17 is actuated by the operation of the pressure actuator 15 in a state where the fixed side electrode 14 is in contact with the second thick plate 103 of the member 100 to be welded. Is moved in the direction of the pressurizing position and is brought into pressure contact with the thin plate 101 to sandwich the welded portion of the member 100 to be welded between the fixed side electrode 14 and the movable side electrode 17 and pressurize and apply the tip of the coil spring 42. 42c is in contact with the thin plate 101 in an annular shape adjacent to the tip of the movable electrode 17, the coil spring 42 is compressed, and the thin plate is formed along the outer periphery of the movable electrode 17 where the tip 42c is pressed by the reaction force of the coil spring 42. A control pressure Fα is applied to 101.

  In this state where the member to be welded 100 is sandwiched and pressed by the fixed electrode 14 and the movable electrode 17 and the control pressure Fα is applied to the thin plate 101 by the coil spring 42, an operation explanatory diagram is schematically shown in FIG. As shown, a pressing force FL by the fixed electrode 14 is applied to the second thick plate 103 of the welded member 100 from below, and a pressing force FL by the movable electrode 17 and a control pressing force Fα by the coil spring 42 are applied to the thin plate 101. Is done. In this case, the sum of the pressing force FL by the fixed electrode 14 acting on the second thick plate 103, the pressing force FU by the movable electrode 17 acting on the thin plate 101, and the pressing force Fα by the coil spring 42 is equal (FL = FU + Fα). ), A pressure FL is applied from the fixed side electrode 14 to the second thick plate 103 to the welded portion of the member 100 to be welded, and from the pressure FL of the fixed side electrode 14 as the pressure FU to the thin plate 101 from the movable side electrode 17. A pressing force having a magnitude obtained by subtracting the control pressing force Fα of the coil spring 42 is applied (FU = FL−Fα).

  By applying a pressure FU of the movable side electrode 17 positioned on the thin plate 101 side smaller than a pressure force FL of the fixed side electrode 14 positioned on the second thick plate 103 side (FU <FL), the movable side electrode 17 is applied. And the fixed electrode 14 are energized, the contact resistance between the thin plate 101 and the first thick plate 102 is relatively increased, the current density is increased, and the first thick plate 102 and the second thick plate 103 are increased. Since the contact resistance between them is kept small, the amount of heat generated between the thin plate 101 and the first thick plate 102 increases relative to the amount of heat generated between the first thick plate 102 and the second thick plate 103. Thus, a good nugget N that melts and is not biased from the thin plate 101 to the second thick plate 103 is formed, and the welding quality is ensured.

  According to this, compared with the control pressurizing application means 20 of the first reference example, the structure of the control pressurization applying means 41 is simple, lightweight and compact, and a spot at a site where the work space is relatively limited. The use of the welding apparatus 40 becomes possible, and the spot welding possible range is expanded. Further, the control pressure Fα can be easily adjusted by changing the specifications such as the repulsive force of the coil spring 42.

(In the form of implementation)
Hereinafter, the implementation of the embodiment of the present invention will be described with reference to FIGS. 12 to 17. FIG. 12 is a configuration diagram of the spot welding apparatus, and FIG. 13 is an explanatory diagram of a main part of the spot welding apparatus. FIG. 14 is a diagram for explaining the operation. 12 to 14, parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 12, 1 is a welding robot, 50 is a spot welding apparatus supported by the welding robot 1, and 110 is a member to be welded that is spot welded.

  Prior to the description of the welding robot 1 and the spot welding apparatus 50, the member to be welded 110 will be described. The welded member 110 is formed by superimposing thin plates on both sides of two superposed thick plates, for example, a first stiff plate 102 having a high rigidity and a first low rigidity on both sides of a superposed second thick plate 103. It is constituted by a four-layered plate set in which the thin plate 101 and the second thin plate 104 are overlapped.

  The welding robot 1 is, for example, an articulated robot, and has a plurality of arms 2 and a wrist 3 attached to the tip of the arm 2, and a spot welding device 50 supported by the wrist 3 via an equalizer unit 4. It is configured to be movable in the three-dimensional direction. Then, the welding robot 1 performs spot welding on the welded member 110 by sequentially moving the spot welding device 50 to each spot position of the welded member 110 held at a predetermined position by a clamper or the like (not shown), that is, a welded portion. .

  The spot welding apparatus 50 includes a base portion 11 that is attached to the wrist portion 3 via the equalizer unit 4. A fixed electrode 14 is attached to the tip of the lower end of a C-shaped yoke 13 attached to the base portion 11.

  A pressure actuator 15 is mounted on the upper end of the base portion 11. A movable electrode 17 is attached to the tip of a rod 16 that reciprocates in the direction of contact with and away from the fixed side electrode 14 coaxially with the fixed side electrode 14 by the pressurizing actuator 15. As a result, the movable side electrode 17 moves to the retracted position of the ascending moving end that is separated from the fixed side electrode 14 by the operation of the pressurizing actuator 15 and the lower moving end that clamps and presses the welded member 110 in cooperation with the fixed side electrode 14. Moves forward and backward between the pressurization position.

  Further, the base 11 is provided with a control pressure applying means 60 for further applying a control pressure to the member 110 to be welded and pressed by the fixed side electrode 14 and the movable side electrode 17.

  As shown in FIGS. 12 and 13, the control pressure applying means 60 separates the rod 16 as shown in the enlarged perspective view of the main part, and a pair of control presses whose base ends are attached to both sides of the base portion 11 on the C-shaped yoke 13 side. Air cylinders 21 and 23 which are pressure actuators are provided. Each air cylinder 21, 23 selectively supplies the air from the air supply source 31 to the expansion side air chamber or the contraction side air chamber via the air supply switching valve 32, so that the cylinder rods 22, 24 expand and contract. In addition, the cylinder rods 22 and 24 are held at the positions by holding air in the contraction-side air chamber or the expansion-side air chamber.

  A welded member 110 is inserted between the tips of the cylinder rods 22 and 24 protruding from the tips of the air cylinders 21 and 23 so as to be inserted with a gap between them, and a lower first connecting plate 61 and an upper The second connection plate 65 is stretched over.

  The central portion of the first connecting plate 61, that is, a belt-like shape in which the base end portion is coupled between the tip ends of the cylinder rods 22 and 24 in the first connecting plate 61 and the tip end portion extends in a direction away from the C-shaped yoke 13 side. The first welded member presser 62 is provided. An electrode insertion portion 63 is formed at the distal end of the first welded member retainer 62, which is cut out in an arc shape or a concave shape into which the movable side electrode 17 and the fixed side electrode 14 can be inserted. A pair of restricting portions 64A and 64B projecting on both sides are formed. Protruding restricting surface pieces 64a and 64b serving as control pressurizing portions are provided on the upper surfaces of the restricting portions 64A and 64B, respectively.

  Similarly, a belt-shaped second welded member presser 66 having a base end portion coupled to the center portion of the second connecting plate 65 and extending in a direction in which the distal end portion is separated from the C-shaped yoke 13 side is provided. The tip of the second welded member holder 66 is formed with an electrode insertion portion 67 that is cut out in an arc shape or a concave shape into which the movable side electrode 17 and the fixed side electrode 14 can be inserted. A pair of restricting portions 68A and 68B projecting on both sides are formed. Protruding restricting surface pieces 68a and 68b serving as control pressurizing portions are provided on the lower surfaces of the restricting portions 68A and 68B, respectively.

The air cylinders 21 and 23 are opposed to the lower surface of the second thin plate 104 of the member to be welded 110 sandwiched between the fixed side electrode 14 and the movable side electrode 17 and the regulating surface pieces 64a and 64b are opposed to each other. Retraction position detection that detects the retraction position that is the expansion / contraction position of the cylinder rods 22 and 24 of the air cylinders 21 and 23 that have a clearance from the upper surface of the first thin plate 101 and that are opposed to the regulation surface pieces 6a and 6b with a clearance. The first and second expansion positions of the air cylinders 21 and 23 in a state where the regulating surface pieces 64a and 64b are in pressure contact with the second thin plate 104 of the member 110 to be welded sandwiched between the sensor S5, the fixed electrode 14 and the movable electrode 17 from below. first pressing position detection sensor S6 for detecting a pressing position, regulating the first thin plate 101 of the welding member 110 sandwiched by the fixed-side electrode 14 and the movable electrode 17 Piece 68a, 68b is provided with a second pressing position detection sensor S7 for detecting a second pressing position is a telescopic position of the air cylinder 21, 23 in the state of being pressed from above.

  The welding robot controller RC stores teaching data of the welding robot 1, and the teaching data includes an operation program for sequentially spot welding the welding points of the member 100 to be welded and spot welding when welding the welding points. The hit point position which is the position and posture of the apparatus 10 is included. Further, the welding apparatus controller WC operates the air supply switching valve 32 based on the operation program of the spot welding apparatus 10 and the detection of the retraction position detection sensor S5, the first pressure position detection sensor S6, and the second pressure position detection sensor S7. Includes control.

  For example, when the retracted position detection sensor S5 detects that the air cylinders 21, 23 are supplied with air to the extension-side air chamber and the air cylinders 21, 23 extend to reach the retracted position, the air is detected based on the detection signal. The supply switching valve 32 is switched to the retracted position to stop the air supply to each extension side air chamber, and the air is held in the extension side air chamber to hold the air cylinders 21 and 23 in the retracted position. The air supply switching valve 32 is switched from the retracted position so that the air in the extension side air chamber is discharged and the air cylinders 21 and 23 that are contracted by the air supplied to the contraction side air chamber have reached the first pressurization position. Is detected by the first pressurization position detection sensor S6, the air supply switching valve 32 is switched to the first pressurization position based on the detection signal, and the air supply into each contraction side air chamber is stopped and the contraction side air is stopped. Air is held in the room, and the air cylinders 21 and 23 are held at the first pressure position. Further, the air supply switching valve 32 is switched from the first pressurizing position to discharge the air in the contraction-side air chamber, and the air cylinders 21 and 23 that are expanded by being supplied with the air into the expansion-side air chamber are second pressurized. When the second pressurization position detection sensor S7 detects that the position has been reached, the air supply switching valve 32 is switched to the second pressurization position based on the detection signal, and the air supply to each expansion side air chamber is stopped. At the same time, the air in the extension side air chamber is held and the air cylinders 21 and 23 are held at the second pressurizing position.

  Next, the operation of the spot welding apparatus 50 will be described with reference to the spot welding apparatus operation process diagram shown in FIG. 14 and FIGS. 15 and 16.

  In spot welding of the member 110 to be welded, according to a preset operation program, in the first welding step, as shown in FIG. 14A, the movable side electrode 17 is at a retracted position away from the fixed side electrode 14 and is given control pressure. When it is confirmed that the retracted position detection sensor S5 of the means 60 has not detected the retracted position of the air cylinders 21, 23, the air supply switching valve 32 is switched by the operation signal from the welding apparatus controller WC, and the air cylinders 21, Air supply into the extension side air chamber 23 starts and the air cylinders 21, 23 extend. When the retracted position detection sensor S5 detects the retracted position during extension, the air supply is stopped there. If not detected, as the air cylinders 21 and 23 are extended, the first welded member presser 62 is lowered until it is below the tip of the stationary electrode 14. Then, the supply of air into the contraction-side air chamber of the air cylinders 21 and 23 is started and the air cylinders 21 and 23 contract. During this time, as shown in FIG. 14B, when the air cylinders 21 and 23 reach the retracted position, the retracted position detection sensor S5 detects, and the air supply switching valve 32 detects the air to the contraction side air chamber of the air cylinders 21 and 23. The supply is stopped, and the first welded member presser 62 and the second welded member presser 66 are held at the retracted position by the cylinder brake.

  Next, when it is confirmed by the detection signal of the retreat position detection sensor S5 that the air cylinders 21 and 23 are at the retreat position, the welding robot 1 is operated and the spot welding apparatus 50 is welded according to a preset program. As shown in FIG. 14 (c), the welded member 110 is joined to the fixed point electrode 14, the movable side electrode 17, the regulating surface pieces 64a and 64b, and the regulating surface pieces 68a and 68b. The fixed side electrode 14 is positioned so as to be in contact with a specified position of the second thin plate 104 corresponding to the hit position.

  In a state where the spot welding device 50 is positioned at the welding position, as shown in FIG. 14C, the tip of the fixed side electrode 24 abuts against the second thin plate 104 of the welded member 110 from below, while the movable side The tip of the electrode 17 and the regulating surface pieces 68a and 68b are opposed to the first thin plate 101 with a gap, and the regulating surface pieces 64a and 64b are opposed to the second thin plate 104 with a gap.

  Next, as shown in FIG. 14 (d), the movable side electrode 17 is pressed from the retracted position by the operation of the pressure actuator 15 with the fixed side electrode 14 in contact with the second thin plate 104 of the member to be welded 110. It is moved in the position direction and is brought into pressure contact with the first thin plate 101. As a result, the pressure applied by the pressurizing actuator 15 acts on the movable side electrode 17 via the movable side electrode 14, the base portion 11, and the C-shaped yoke 13, and the pressure is applied between the movable side electrode 17 and the fixed side electrode 14. The welded portion of the welding member 110 is clamped and pressurized.

  On the other hand, the air supply switching valve 32 is switched to discharge the air in the expansion side air chamber of the air cylinders 21 and 23 and the air is supplied to the contraction side air chamber so that the air cylinders 21 and 23 are contracted to be first welded. The member presser 62 and the second welded member presser 66 are raised, and the restriction surface pieces 64 a and 64 b provided on the upper surface of the first welded member presser 62 are adjacent to the tip of the fixed electrode 14 and the welded member 110. When the air cylinders 21 and 23 that are in pressure contact with the second thin plate 104 from below and reach the first pressurization position reach the first pressurization position, the first pressurization position detection sensor S5 detects, and the air supply switching valve 32 detects the first pressurization position. The air supply to the contraction side air chamber of the air cylinders 21 and 23 is stopped and the air is held in the contraction side air chamber.

  FIG. 15 shows a state in which the member to be welded 110 is sandwiched and pressed by the fixed side electrode 14 and the movable side electrode 17 and the second thin plate 104 is pressurized by the restriction surface pieces 64 a and 64 b by the air cylinders 21 and 23. As shown in the operation explanatory diagram, a pressing force FL by the fixed side electrode 14 is applied to the second thin plate 104 of the member 110 to be welded from below, and a pressing surface FU by the movable side electrode 17 and a regulating surface by the air cylinders 21 and 23. A first control pressure Fα by the pieces 64 a and 64 b is applied to the second thin plate 104 adjacent to the tip of the fixed side electrode 14.

  In this case, as schematically shown in FIG. 15, the pressurizing force of the pressurizing actuator 15 acts on the fixed electrode 14 via the movable electrode 17, the base portion 11 and the C-shaped yoke 13 to control the cylinders 21 and 23. The applied pressure acts on the regulating surface pieces 64 a and 64 b, and the sum of the applied pressure FL by the fixed side electrode 14 acting on the second thin plate 104 and the first controlled pressure Fα by the regulating surface pieces 64 a and 64 b and the movable side electrode 17. The applied pressure FU acting on the first thin plate 101 becomes equal (FU = FL + Fα). Thereby, the member 110 to be welded is clamped in a stable state by the fixed electrode 14, the movable electrode 17, and the regulating surface pieces 64a and 64b.

  On the other hand, a pressure FU is applied from the movable electrode 17 to the first thin plate 101 to the welded part of the member 110 to be welded, and a pressure applied by the movable electrode 17 as a pressure FL from the fixed electrode 14 to the second thin plate 104. A pressing force having a magnitude obtained by subtracting the first control pressing force Fα by the regulating surface pieces 64a and 64b from the FU is applied (FL = FU−Fα).

  In this way, the applied pressure FL by the fixed electrode 14 is smaller than the applied pressure FU of the movable electrode 17 (FL <FU).

  Next, the member 110 to be welded is sandwiched and pressed by the fixed side electrode 14 and the movable side electrode 17, and the control pressing force is applied by the restriction surface pieces 64 a and 64 b, so that the fixed side electrode 14 positioned on the second thin plate 104 side is applied. In a state where the pressing force FL is applied to be smaller than the pressing force FU of the movable side electrode 17 positioned on the first thin plate 104 side, a predetermined time is provided between the movable side electrode 17 and the fixed side electrode 14 as shown in FIG. Energize and weld. In this welding, when a current is passed between the movable side electrode 17 and the fixed side electrode 14, the current density at the joint between the second thin plate 104 and the second thick plate 103 is large, and the amount of heat generated is the first thin plate 101 and the first thickness. It increases relatively with respect to the amount of heat generated at the joint portion of the plate 102, and extends from the joint portion between the second thin plate 104 and the second thick plate 103 to the joint portion between the first thick plate 102 and the second thick plate 103. A good nugget N1 having a large penetration amount is formed, and the welding strength between the second thin plate 104 and the second thick plate 103 can be ensured.

  When this welding is completed, in the second welding step, the air supply switching valve 32 is switched as shown in FIG. 14 (f) to discharge the air in the contraction side air chamber of the air cylinders 21 and 23 and to the extension side air chamber. Is supplied and the air cylinders 21 and 23 are extended so that the first welded member retainer 62 descends and separates from the second thin plate 104 of the welded member 110, while the second welded member retainer 66 descends and restricts the control surface. When the pieces 68a and 68b are in pressure contact with the first thin plate 101 of the member 110 to be welded from above and adjacent to the tip of the movable electrode 17, and the air cylinders 21 and 23 that extend further reach the second pressurizing position, the second pressurizing position is reached. The pressure position detection sensor S7 detects, the air supply switching valve 32 is switched to the second pressurizing position, the air supply to the extension side air chamber of the air cylinders 21, 23 is stopped, and the air supply to the extension side air chamber is stopped. To hold.

  FIG. 16 shows a state in which the member to be welded 110 is sandwiched and pressed by the fixed side electrode 14 and the movable side electrode 17 and the first thin plate 101 is pressurized by the restriction surface pieces 68a and 68b by the air cylinders 21 and 23. As shown in the operational explanatory diagram, a pressing force FL by the fixed side electrode 14 is applied to the second thin plate 104 from below, and by a pressing force FU by the movable side electrode 17 and restriction surface pieces 68a and 68b by the air cylinders 21 and 23. A second control pressure Fβ is applied to the first thin plate 101.

  In this case, the applied pressure FL by the fixed side electrode 14 acting on the second thin plate 104 is equal to the applied pressure FU of the movable side electrode 17 acting on the first thin plate 101 and the second control applied pressure Fβ by the regulating surface pieces 64a and 64b. It becomes equal to the sum (FL = FU + Fβ). Thereby, the member 110 to be welded is clamped in a stable state by the fixed electrode 14, the movable electrode 17, and the regulating surface pieces 68a and 68b.

  On the other hand, a pressure FL is applied from the fixed electrode 14 to the second thin plate 104 to the welded part of the member 110 to be welded, and a pressure applied by the fixed electrode 14 from the movable electrode 17 to the first thin plate 101 as a pressure FU. A pressing force having a magnitude obtained by subtracting the second control pressing force Fβ by the regulating surface pieces 68a and 68b from the FL is applied (FU = FL−Fβ).

  Thus, the pressure FU applied by the movable electrode 17 is smaller than the pressure FL applied by the fixed electrode 14 (FU <FL).

  The movable side electrode located on the first thin plate 101 side by sandwiching and applying pressure to the welded member 110 by the fixed side electrode 14 and the movable side electrode 17 and applying the second control pressure by the regulating surface pieces 68a and 68b. 17 is applied between the movable electrode 17 and the fixed electrode 14 as shown in FIG. 14G in a state where the applied pressure FU of 17 is applied to be smaller than the applied pressure FL of the fixed electrode 14 positioned on the second thin plate 104 side. Energize for a predetermined time and weld. In this welding, when current is passed between the movable side electrode 17 and the fixed side electrode 14, the current density at the junction between the first thin plate 101 and the first thick plate 102 is the junction between the second thin plate 104 and the second thick plate 103. And a good nugget N2 having a large amount of penetration is formed at the joint between the first thin plate 101 and the first thick plate 102, and the welding strength of the first thin plate 101 and the first thick plate 102 is increased. It can be secured.

  That is, in the first welding process, the contact pressure between the second thin plate 104 and the second thick plate 103 is reduced, and a current is passed between the movable side electrode 17 and the fixed side electrode 14 to positively contact the second thin plate 104 and the second thick plate 104. The nugget N1 is formed between the two thick plates 103 to ensure the welding strength. After that, in the second welding step, the contact pressure between the first thin plate 101 and the first thick plate 102 is reduced to reduce the movable side electrode 17 and The first thin plate 101 and the first thick plate are energized by energizing between the fixed side electrode 14 and positively forming the nugget N2 at the contact point with the first thin plate 101 and the first thick plate 102 to ensure the welding strength. 102, the second thick plate 103, and the second thin plate 104 can be welded, and the welding strength of the welded portion of the four-layered member 110 to be welded can be secured, so that the welding quality can be secured.

After this welding is completed, as shown in FIG. 14 (h), the movable side electrode 17 is moved from the pressure position to the retracted position by the operation of the pressure actuator 15, and the fixed side electrode 14 and the movable side electrode 17 are used. The clamping of the member to be welded 110 is released. On the other hand, the air cylinder supply switching valve 32 is switched to discharge air in the expansion side air chamber of the air cylinders 21 and 23 and supply air to the contraction side air chamber to contract the air cylinders 21 and 23. When the air cylinder 21, 23 reaches the retracted position to shrink, retreat avoid position sensor S5 detects the air of the air supply switching valve 32 to the contracted side air chamber of the air cylinder 21, 23 is switched to the retracted position The supply is stopped and the air in the contraction side air chamber is held. Thereby, the 1st to-be-welded member presser 62 and the 2nd to-be-welded member presser 66 are hold | maintained in a retracted position.

  Next, when it is confirmed by the detection signal of the retracted position detection sensor S5 that the air cylinders 21 and 23 are at the retracted position, the welding robot 1 is operated and the spot welding device 50 is moved to the spot position of the member 110 to be welded. And is moved to the hit position of the next member 110 to be welded.

  According to the present embodiment configured as described above, a four-layer structure in which the first thin plate 101 and the second thin plate 104 having low rigidity are superimposed on both surfaces of the first thick plate 102 and the second thick plate 103 having high rigidity. A spot welding device 50 for spot welding a member to be welded 110 constituted by a plate assembly includes a fixed side electrode 14 provided on the base portion 11 via a C-shaped yoke 13 and a pressure actuator provided on the base portion 11. 15, a movable side electrode 17 that is in contact with and away from the fixed side electrode 14, and a welding position in the vicinity of the welding position of the first thin plate 101 and the second thin plate 104 of the member 100 to be welded and pressed by the fixed side electrode 14 and the movable side electrode 17. A control pressure applying means 60 for selectively applying a control pressure is provided, which is sandwiched and pressurized by the fixed side electrode 14 and the movable side electrode 17 and applied with the pressure FL by the fixed side electrode 14. Then, the contact pressure between the second thin plate 104 and the second thick plate 103 is increased by applying the pressurizing force FU by the movable electrode and applying the first control pressure Fα in the vicinity of the welding position of the second thin plate 104. The amount of heat generated at the junction between the second thin plate 104 and the second thick plate 103 is controlled to be smaller than the contact pressure between the thick plate 102 and the first thin plate 101 and the movable side electrode 17 and the fixed side electrode 14 are energized. It increases relative to the amount of heat generated at the joint between the plate 102 and the first thin plate 101. Therefore, the welding strength between the second thin plate 104 and the second thick plate 103 is ensured.

  Similarly, by applying the second control pressure Fβ to the first thin plate 101, the contact pressure between the first thin plate 101 and the first thick plate 102 becomes smaller than the contact pressure between the second thick plate 103 and the second thin plate 104. When the movable side electrode 17 and the fixed side electrode 14 are energized, the current density at the junction between the first thin plate 101 and the first thick plate 102 is larger than the current density at the junction between the second thick plate 103 and the second thin plate 104. Relatively increase. Therefore, the welding strength of the 1st thin plate 101 and the 2nd thick plate 102 is ensured, and the 1st thin plate 101 and the 2nd thin plate 104 with low rigidity are piled up on both surfaces of the 1st thick plate 102 and the 2nd thick plate 103 with high rigidity. It is possible to ensure the welding quality of the welded member 110 constituted by the four-layered plate assembly. In particular, without being affected by the clamping position at which the member 110 to be welded is clamped, the fixed side electrode 14 and the movable side electrode 17 are sandwiched and pressurized to apply the pressure FL by the fixed side electrode 14 and the pressure FU by the movable side electrode. In addition, it is possible to apply a control pressure in the vicinity of the welding position of the member 110 to be welded, and a good nugget is formed from the first thin plate 101 to the second thin plate 104 at various welding positions. 1 The welding strength of the thin plate 101 can be ensured.

  Note that the present invention is not limited to this embodiment, and various modifications can be made without departing from the spirit of the invention. For example, in the above-described embodiment, the case where the air cylinders 21 and 23 are used as the control pressure actuators has been described as an example. However, a servo motor or the like may be used.

  Moreover, although the case where it formed with the protruding regulation surface piece 64a, 64b, 68a, 68b as a control pressurizing part was demonstrated to the example, it can change variously according to the shape etc. of the member 110 to be welded. For example, as shown in FIG. 17 corresponding to FIG. 13, the restricting portion 64 </ b> A formed along the electrode insertion portion 63, which is cut out in an arc shape or a concave shape at the distal end portion of the first welded member presser 62. In addition, a semicircular arc-shaped regulating surface piece 70 projecting upward along the electrode insertion portion 63 and an electrode insertion portion 67 cut out in a circular arc shape or a concave shape at the tip of the second welded member presser 66 on the upper surface of 64B. Can be formed by a semicircular arc-shaped regulating surface piece 71 projecting downward along the electrode insertion portion 67 on the lower surface of the regulating portions 68A and 68B formed along.

In the form of implementation, the desired control pressure F.alpha, thickness and pressure FL of Fβ pressurized applying position the resulting weld members, calculated in advance based on the FU, the regulating surface pieces Although the air cylinder is controlled so that the position becomes the pressure applying position, the control pressure applying means can obtain desired control pressures Fα and Fβ from the regulating surface piece as the control pressurizing unit. If so, it is possible to control the amount of air supplied to the air chamber of the air cylinder and the air pressure as parameters, or to control while directly detecting the pressure between the regulating surface piece and the thin plate. .

DESCRIPTION OF SYMBOLS 1 Welding robot 10 Spot welding apparatus 11 Base part 13 C type yoke 14 Fixed side electrode (1st welding electrode)
15 Pressure actuator 16 Rod 17 Movable electrode (second welding electrode)
20 Control pressure applying means 21, 23 Air cylinder (Control pressure actuator)
22, 24 Cylinder rod 25 Connecting plate 26 Welded member holder 26a Base end portion 28a, 29a Restricting surface piece (control pressurizing portion)
28b, 29b Regulating surface piece (control pressure unit)
28A, 28B Regulating surface piece (control pressure unit)
40 Spot Welding Device 41 Control Pressurizing Applying Unit 42 Coil Spring 42b Base End 42c Tip 50 Spot Welding Device 60 Control Pressurizing Applying Unit 61 First Connection Plate 65 Second Connection Plate 62 First Welded Member Pressers 64a and 64b Regulating surface piece (control pressure unit)
66 2nd to-be-welded member presser 66a Base end part 68a, 68b Control surface piece (control pressurizing part)
70, 71 Restricting surface piece (control pressure unit)
100 welded member 101 thin plate (first thin plate)
102 1st thick plate 103 2nd thick plate 104 2nd thin plate 110 to-be-welded member

Claims (7)

The first thin plate and the second thin plate, the first thick plate and the second thick plate having a larger thickness than the first thin plate and the second thin plate, the first thin plate, the first thick plate, the second thick plate, and the second thin plate. In the spot welding method of spot welding the welded members that are stacked in order,
A first welding electrode that contacts the second thin plate, a first control pressure unit that contacts the second thin plate adjacent to the first welding electrode, and the first thin plate facing the first welding electrode. A first welding step of sandwiching and pressurizing the member to be welded by a second welding electrode in contact, and conducting spot welding by energizing between the second welding electrode and the first welding electrode in the sandwiched and pressurized state;
Maintaining the clamped state of the member to be welded by the first welding electrode and the second welding electrode, the first control pressurizing part is separated from the second thin plate and adjacent to the second welding electrode on the first thin plate. The second control electrode is brought into contact with the first welding electrode, the second welding electrode, and the second control electrode by the second control pressure unit. And a second welding step in which spot welding is performed by energizing between the two and a spot welding method. The pressure applied to the second thin plate by the first welding electrode in the clamping pressure state in the first welding step is FL, and the control pressure applied to the second thin plate by the first control pressure unit is Fα, when the applied pressure applied to the first thin plate by the second welding electrode is FU,
FU = FL + Fα
And
In the second welding step, the pressing force applied to the second thin plate by the first welding electrode in the clamping pressure state is FL, the pressing force applied to the first thin plate by the second welding electrode is FU, 2 When the second control pressure applied to the first thin plate by the control pressurizing unit is Fβ,
FL = FU + Fβ
The spot welding method according to claim 1 , wherein: The first thin plate and the second thin plate, the first thick plate and the second thick plate having a thickness greater than that of the first thin plate and the second thin plate are the first thin plate, the first thick plate, the second thick plate, and the second thin plate. In the spot welding device that spot welds the workpieces that are stacked in the plate order,
A first welding electrode facing the second thin plate;
A second welding electrode that is coaxial with the first welding electrode and opposes the first thin plate of the welding member to clamp and press the member to be welded in cooperation with the first welding electrode;
A first control pressure unit that applies a first control pressure to the second thin plate adjacent to the first welding electrode and a second control pressure to the first thin plate adjacent to the second welding electrode. A second control pressure unit,
The member to be welded is sandwiched and pressurized by a first welding electrode and a first control pressure unit that contact the second thin plate and a second welding electrode that faces the first welding electrode and contacts the first thin plate, Spot welding by energizing between the second welding electrode and the first welding electrode in a sandwiched pressure state,
The member to be welded is sandwiched and pressurized by a first welding electrode that contacts the second thin plate, a second welding electrode that faces the first welding electrode and contacts the first thin plate, and a second control pressure unit, A spot welding apparatus, wherein spot welding is performed by energizing between the second welding electrode and the first welding electrode in a sandwiched pressure state. The first thin plate and the second thin plate, the first thick plate and the second thick plate having a larger thickness than the first thin plate and the second thin plate, the first thin plate, the first thick plate, the second thick plate, and the second thin plate in this order. In a spot welding apparatus for spot welding the overlapped workpieces to be welded,
A base part;
A first welding electrode supported by the base portion and in contact with the second thick plate;
The second welding electrode is supported on the base portion with a rod interposed therebetween, and the second welding electrode is brought into contact with the first thin plate to cooperate with the first welding electrode to sandwich the member to be welded. A pressure actuator that moves between a pressure position that applies pressure to the welded member and a retracted position that is separated from the welded member;
A first control pressure unit that applies a first control pressure to the second thin plate adjacent to the first welding electrode of the member to be welded and a first thin plate adjacent to the second welding electrode of the member to be welded. A control pressurizing application means having a second control pressurizing unit for applying 2 control pressurizing force,
The member to be welded is sandwiched and pressurized by a first welding electrode and a first control pressure unit that contact the second thin plate and a second welding electrode that faces the first welding electrode and contacts the first thin plate, Spot welding by energizing between the second welding electrode and the first welding electrode in the sandwiched pressure state,
The member to be welded is sandwiched and pressurized by a first welding electrode that contacts the second thin plate, a second welding electrode that faces the first welding electrode and contacts the first thin plate, and a second control pressure unit, A spot welding apparatus, wherein spot welding is performed by energizing between the second welding electrode and the first welding electrode in a sandwiched pressure state. The control pressure applying means includes the first control pressure unit,
The second control pressure unit;
The first control pressurization unit and the second control pressurization unit are mounted on the base unit and support the first control pressurization unit and the second thin plate adjacent to the first welding electrode. A first pressurizing position for applying the first control pressure and separating the second control pressurizing unit from the first thin plate; and the second control pressurizing unit separates from the second thin plate and the second control pressurizing unit. And a control pressurizing actuator that is selectively moved to a second pressurizing application position that abuts the first thin plate adjacent to the second welding electrode and applies the second control pressurizing force. The spot welding apparatus according to claim 4 . The control pressure actuator is
An air cylinder mounted on the base part,
6. The spot welding apparatus according to claim 5 , wherein the first control pressurizing unit and the second control pressurizing unit are disposed apart from each other at the tip of a cylinder rod of the air cylinder. The control pressure actuator is
A pair of air cylinders mounted in parallel with the base portion;
A first connection plate and a second connection plate that are spanned between the tips of the cylinder rods of the air cylinders;
A first welded member presser having a base end connected to the first connecting plate and extending in the direction of the first welding electrode and having the first control pressurizing unit disposed at the tip;
A second welded member presser having a base end connected to the second connecting plate and extending in the direction of the second welding electrode and having the second control pressurizing unit disposed at the tip. The spot welding apparatus according to claim 6 , characterized in that:

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